[Cashtab] Send token amount input field css patch

Summary: Related to task T2343 The ant-input-suffix in the DestinationAmount field on the send token page was rendering the font black, it has been patched to show up as the correct color.

Test Plan:
cd web/cashtab-v2
npm start
navigate to SendToken
observe that the token ticker in the DestinationAmount component is the correct color

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D11285